How Will the Freeze Impact Olive Bloom?

All eyes have been on almonds during the recent cold snap, but the recent weather has reminded Bill Krueger, Farm Advisor Emeritus in Glenn County, of a similar cold snap in 2006 and the resulting damage to olive bloom. Here I have republished an article Bill wrote of his 2006 olive bloom observations:

Olive Bloom Observations
Bill Krueger, 2006

At this time, it does not look like [heavy bloom and cropping] will happen, especially with the Manzanillo variety. Generally, the Manzanillo bloom is sparse to non-existent. Many of the flower buds are not developing. In many cases, the small undeveloped buds can be seen at the leaf axils. They often appear brown and dry and can be flicked off. The severity of the problem is variable. There appears to be a geographical gradient from north to south, with the problem being more severe in the north and getting somewhat less as you go south. The problem is most severe on Manzanillo. Most Sevillanos and Missions that I have seen around Orland appear to have a normal bloom.

What is responsible for this unexpected situation? The frost we experienced in February is suspected. From February 15th to February 21st, we experienced freezing minimum temperatures with lows around 25oF. Again on March 10, we had freezing minimum temperatures. Normally low temperatures like these would not be expected to cause much damage and nobody I know thought it necessary to frost protect. I have seen freeze damage in the past in December or January which caused defoliation, but did not kill the flower buds. At bloom time, defoliated shoots had blooming flowers which, of course, did not persist to harvest.

Evidence to support the hypothesis that this is frost damage includes an orchard in southern Tehama County that has a reasonable bloom only in 4 rows that were flood irrigated during the freezing conditions. Well water in excess of what was necessary to run microsprinklers in an adjacent almond block was run down these rows. The rest of the orchard which was not protected has limited bloom. In some orchards, a better bloom has been observed in higher areas of the orchard than in lower areas. This is consistent with the colder heaver air settling in lower areas and has been seen in other years on other crops experiencing frost damage. Another factor that may have influenced the outcome was the unseasonably warm temperatures that we experienced for at least a week prior to the frosts. At the time of the frost, crop development on other crops such as almonds was 7 to 10 days ahead of normal. It may be that this warm weather increased the physiological activity in the [olive flower] buds and increased their frost susceptibility.

Unseasonably warm weather followed by a week of freezing weather? I can see why the conditions this year reminded Bill Krueger of 2006. We’ll have to watch and see what the impact on olive bloom will be this spring.